The invention relates to a valve means comprising a valve housing, which delimits a control chamber, into which a plurality of fluid ducts open and in which a control rocker member is arranged serving for the control of at least one of the fluid duct openings and adapted to be pivoted between at least two terminal positions, its pivotal position being able to be influenced by an electrically activated flexible element, which is adapted to act on an actuating portion of the control rocker member.
A valve means of this type is disclosed in the European patent publication 0 741 248 A2. Here a control chamber is defined in the interior of the valve housing, in which a pivotally moving control rocker member is arranged, whose actuating portion, which constitutes an extension of the pivot axis, projects from the control chamber of the valve housing. It is possible, for instance, for a piezoelectric flexible element to act on the actuating portion in order to influence the position of pivoting of the control rocker member, which in the interior of control chamber is opposite to two fluid duct openings or ports which it is able to open and close in a manner dependent on the position of pivoting. A similar valve means is also disclosed in the German patent publication (utility model) 29,901,855, in which case however, departing from the design of the said European patent publication 0 741 248 A2 the fluid ducts to be controlled are placed on a longitudinal side of the control rocker member.
In the case of these two known valve means extensive seal means are necessary in order to enable the actuating portion to extend out of the control chamber without leakage and while ensuring pivotal mobility. Furthermore, a mechanical biasing effect on any piezoelectric flexible element employed for operation is needed in order to bias the control rocker member in the home position into one of its two terminal positions. Mechanical relaxation of the flexible element may mean that functional defects occur.
A similar problem arises in the case of valve means in accordance with the U.S. Pat. No. 5,779,218, wherein for setting a predetermined terminal position the piezoelectric flexible element is subjected to a biassing force and then cast in the position assumed.
Therefore there has already been a suggestion in the European patent publication 0 547 022 B1 to deal with the relaxation problem by means of a mechanical spring acting on the piezoelectric flexible element for compensation. However this leads to a greater overall height of the valve means.
One object of the present invention is to create a valve means of the type initially mentioned, in the case of which the relaxation problem is dealt with, at least to a substantial extent, using a simple and compact valve structure.
In order to achieve these and/or other objects appearing from the present specification, claims and drawings, in the present invention the control rocker member including its actuating portion is accommodated in the control chamber and is biased by spring means without involvement of the flexible element into a first one of the two terminal positions, the flexible element in a non-electrically-excited condition within the control chamber being substantially free of mechanical stress and without spring bias, engaging the actuating portion of the control rocker member in the first terminal position of said member.
This means that when the flexible element is deactivated the control rocker member is biased toward a terminal position, the spring forces employed for this being transmitted to the control rocker member independently of the flexible element so that the flexible element itself can engage the control rocker member when it is essentially free of mechanical stresses and therefore of relaxation and no spring bias, acting on the flexible element, is required for compensation of any relaxation tendency. The valve means may consequently be relatively simply assembled, because the flexible element may be installed completely free of bias or at least with only a small bias, something which may take place simply by laying it in place. Since furthermore the flexible element cooperates within the control chamber with the control rocker member, there are no problem sealing areas between the control rocker member and the valve housing. The valve means may all in all be designed with extremely compact dimensions.
Further advantageous developments of the invention are defined in the claims.
As an electrically activated flexible element use is more particularly made of a piezoelectric flexible element, such a flexible element of memory metal or of bimetal also being possible in principle.
On the basis of the valve means it is possible to create different types of valve inexpensively, as for example valves with a xe2x80x9cnormally closedxe2x80x9d characteristic and a xe2x80x9cnormally openxe2x80x9d characteristic.
In the case of a preferred embodiment the control chamber has two fluid openings controlled by the control rocker members, which each communicate with a separate fluid duct and which close and open alternatingly in the two terminal positions of the control rocker member, the closure of one respective fluid duct opening causing simultaneous clearing of the respectively other fluid duct opening. In this respect the two controlled fluid duct openings are preferably controlled by different rocker arms of the control rocker member and therefore, in the case of there being a multi-part valve housing, they can be arranged on the same housing part on the same side of the control rocker member.
It is convenient for the control rocker member to bear a sealing material layer in the portion cooperating with the respective fluid duct opening for control, the control rocker member preferably being borne in a pivotally movable fashion on a fulcrum point on the housing and in the pivotal supporting part has a material layer identical to the layer of sealing material as regards material and thickness, such material layer being more particularly made coherently with the layer of sealing material. This means that any swelling of the sealing material will not have any effect on the valve gap present between the control rocker member and the valve duct opening to be controlled. Since swelling of the sealing material simultaneously results in identical swelling of the material layer present in the supporting portion, there is merely a parallel displacement of the control rocker member, something which is practically devoid of effect on the valve gap.
It is convenient for the arrangement to be such that starting at a point of attachment, which as regards the control rocker member is spaced transversely from its pivot axis, the flexible element extends toward the control rocker member, it partially overlapping the control rocker member on the side opposite to the at least one fluid opening to be controlled. The actuating portion, cooperating with the flexible element, of the control rocker member may here be arranged on the side, opposite to the point of attachment, of the pivot axis at a distance from same. In this respect there is a preferably a provision such that the spring means on the side, opposite to the actuating portion, of the pivot axis engage the rocking control member.
In this respect there is preferably a provision such that by having different lever lengths an optimum adaptation to the stroke-force characteristic of the flexible element may be achieved.
The point of attachment of the flexible element may in case of need be arranged directly within the control chamber. In the case of a design, which is also advantageous, the point of attachment is located in an attachment chamber, adjacent to the control chamber, in the valve housing, from which the front terminal section of the flexible element extends into the control chamber. The attachment chamber may for example be filled with a potting or casting composition in order to lock the flexible element in position and simultaneously to create a seal for the electrical connections.
It is furthermore an advantage if the home position assumed in the electrically non-excited condition, by the flexible element corresponds to that position, which the flexible element assumes on assembly of the valve means simply on the basis of its weight, after it has been placed on the actuating portion of the control rocker member and on at least one fulcrum point on the housing. In this case it is possible to achieve fitting of the flexible element free effects due to manufacturing errors, without play and free of the need for later adjustment, simply on the basis of its own weight.
The spring means predetermining the selected terminal position of the control rocker member are preferably arranged directly in the control chamber. In this respect the spring means may be so designed that they simultaneously perform a holding function for the control rocker member. It is more particularly an advantage for the spring means to act on the control rocker member with a spring force parallel to the actuating force of the flexible element.
In the case of a form of the invention, which is particularly simple to manufacture, the spring means comprise at least one spring lug anchored at one end on the housing and at the other end on the control rocker member, the spring lug being part of a spring unit, which is able to be secured to the housing by way of an anchoring section. It is convenient for the entire spring unit, in the case of which the anchoring section and the spring lug are preferably made integral, to be fashioned of resiliently elastic material, for example of spring steel.
In the case of a further embodiment of the spring means the spring force employed for biasing the control rocker member is obtained using torsion rod elements aligned in the same direction as the pivot axis and which extend between control rocker member and the valve housing and which are preferably able to define the pivot axis directly. The attachment of the torsion rod element on the housing can be using attachment parts, which are held between the holding faces of two parts of the valve housing. Here it is possible for the control rocker member, the torsion rod elements and the attachment parts to be designed in the form of an integral component group. Furthermore, the arrangement is preferably such that the holding valve housing so act upon the attachment parts that on the one hand the control rocker member is urged into the first terminal position and on the other hand there is an additional twist of the torsion rod elements in order to produce the desired biasing force.
The holding faces cooperating with a respective attachment part are best installed on the one hand on a bottom part and on the other hand on a top part of the valve housing, the bias being obtained directly on assembly of the two housing parts.
The flexible element can be a component of a drive means for the control rocker member, which furthermore has means in order to permit a step by step pivoting of the control rocker member, the corresponding means defining for instance a ratchet mechanism or a self-locking mechanism. This means that it is possible to use relatively small setting forces of the flexible element and small pivoting strokes of the flexible element to serve large valve seat diameters with the resulting large setting forces and opening strokes. In this respect the design may be such that after a single operation by the flexible element the control rocker member opens by one pivotal step and after renewed operation closes again in order to realize a bistable valve function.
Taken together the control rocker member and the associated spring means can be termed a first control unit. In addition to this first control unit a suitably designed second control may be present, which serves to control at least one further fluid opening or port, the control rocker members of both control units being able to be actuated jointly by the flexible element. Then the design may be such for instance that the valve means performs a 3/3 valve function. Preferably, the second control rocker member is arranged in a bilaterally symmetrical manner in relation to the first control rocker member on the opposite side of the flexible element.
It is an advantage for adjustment means to be present, which render possible a variable presetting of the position, assumed in relation to the fluid duct openings to be controlled, of the pivot axis of the control rocker member. The valve gap may be adjusted in this way. This can preferably also be performed even without the flexible element during assembly of the valve means and is more especially appropriate, when the valve means possesses two control rocker members.
If means are present, which render possible a stepless application of the actuating voltage for the flexible element, it is extremely simple to provide for any continuous control of the control rocker member, any desired positions of pivoting being able to be preset as required.
Further advantageous developments and convenient forms of the invention will be understood from the following detailed descriptive disclosure of several embodiments thereof in conjunction with the accompanying drawings.